How to Compare Two Screenshots and Spot Every Difference

The problem with comparing screenshots by eye

You have a “before” screenshot and an “after” screenshot. They look almost the same — but something changed. A button moved three pixels. A colour shifted slightly. An icon went missing in one corner. Staring at two images side by side, switching back and forth, is slow and unreliable. Your eye misses small differences, and it certainly can’t tell you exactly where they are.

There’s a better way: let a tool do the pixel-level comparison for you.

Compare two screenshots in three steps

DiffALL compares two images automatically and shows you every difference:

Upload both screenshots — the expected version and the actual one.
Get an instant similarity score from 0 to 100, based on SSIM (Structural Similarity Index) — a metric designed to match how humans perceive visual change.
Read the heatmap. A colour overlay highlights exactly which regions differ — calm blue where the images match, hot red where they don’t. A marker is drawn around each changed area so you can’t miss it.

No install, no sign-up for your first comparison.

What the results tell you

SSIM score — the headline number. Above 95% means the screenshots are nearly identical; a lower score means real differences are present.
PSNR — a second quality metric, useful for spotting compression artefacts.
The heatmap — the where. Even a 99% similar pair will light up the one region that actually changed, so you can jump straight to it.

Handling screenshots that aren’t pixel-aligned

Sometimes two screenshots are of the “same” screen but captured at slightly different sizes or positions — so a naive pixel comparison would flag the whole image as different. DiffALL’s flexible mode aligns the two images first (using feature detection) before comparing, so you only see genuine content changes, not framing noise.

Common use cases

Visual QA — confirm a UI change didn’t break anything else on the page.
Design review — verify the implemented screen matches the mockup.
Regression testing — catch unintended visual changes between releases (and you can automate this with the DiffALL API in your CI pipeline).
Bug reports — attach a shareable link to the diff instead of a vague “it looks off.”

Try it now

Stop switching between two tabs hunting for what changed. Upload your two screenshots and let DiffALL point at every difference for you.